This invention is concerned with a position indicator for valves and the like.
In valves, but also in other devices, it is often desirable-- or even necessary-- to be able to tell the position of a member, e.g. of a valve member. Several ways have been proposed in the art for doing this.
One proposal in German Pat. No. 805,477 suggests that a valve spindle, which moves axially in one direction or in an opposite direction as the valve is progressively opened or closed, carry a sleeve which is provided with markings and extends into a stationarily mounted ring. The position of the valve member which moves with the spindle is indicated in dependence upon the extent to which the ring covers the sleeve and the markings thereon. This arrangement provides an approximate indication of the valve member position, but it requires a mental conversion of the sleeve/ring indication into the actual valve member position. This requires considerable skill and the arrangement can therefore be used with any degree of reliability only by personnel having this skill and trained in the use of the arrangement.
German Pat. No. 646,316 teaches a different construction, wherein an indicating arrangement is provided in a handwheel for valves having a spindle which rises and descends in dependence upon the direction in which it is turned. A shaft is journalled in the housing, the latter being configurated as the handwheel. This shafts acts as a lever and is supported against a rod that is mounted outside the housing but extends movably into the same. The lever moves with the spindle and undergoes an angular displacement which is transmitted to an indicating arrangement via an angle drive. This construction is complicated and therefore subject to malfunction. Also, the rod extending to the outside of the housing can cause accidents.
Finally, another proposal suggests to use an end portion of the moving spindle itself to provide a positional indication. This proposal is not satisfactory for various reasons, including the fact that viewing must take place at an angle of 90.degree. relative to the spindle axis, because otherwise the indications either cannot be seen at all or are so distorted that they transmit wrong information.